This invention relates to an electric drive with two motors on a common lamination stack, each motor of which can be connected separately to a single phase A.C. line serving as the only supply source, in general and more particularly to an improved drive of this nature.
Drives of this type which include a stator winding of a commutator motor which has a small number of poles (lower pole number) on the one hand and of an induction motor which has a larger number of poles (higher pole number), on the other hand, arranged in a common stator lamination stack are known. Such drives include a common armature wound in such a manner that, for operation as an induction motor, short circuits with a number of poles corresponding to that of the exciting induction motor stator field are formed from series connected coils in each phase winding, and that, for commutator motor operation, circuits with a number of poles corresponding to the exciting commutator stator field are formed via the segments of a commutator. Hereinafter this type of drive will be referred to as a two motor drive.
In one known two motor drive of this type (German Offenlegungsschrift No. 25 30 294), the stator lamination stack is slotted over the entire circumference; a 12 pole, 3 phase stator winding of an induction motor and a winding of a 2 pole commutator motor, provided as an A.C. series motor, are arranged in common respective slots. A stator lamination cut with unequal slot cross section is chosen and the winding of the induction motor is distrubuted uniformly over all slots, while the winding of the series motor only partially occupies slots which, for this purpose, have a larger slot cross section than the other slots which are occupied only by the winding of the induction motor. Both a 2 pole armature winding for the series motor, connected to the segments of a commutator, and a 2 phase wound induction motor winding, completely insulated from the former, with a number of poles corresponding to the number of poles of the induction motor winding of the stator, are provided in the rotor. The coils or groups of coils of the 2 phase induction motor winding are connected in series in each phase and form short circuits due to the beginning and the end of the series circuit being joined together.
In another known two motor drive (Swiss Pat. No. 17 611) with a D.C. motor and an A.C. motor comprising an induction motor winding connected to the commutator and a D.C. wave winding, the drive, which can be used mainly as a rotary converter, is always operated simultaneously with A.C. and D.C.